An 'Unloved' Grass May Turn Hero In the Struggle Against Soil Erosion

VETIVER, a tall grass whose long, fragrant roots are commonly used in perfumes and soaps, could serve as an inexpensive and effective barrier against soil erosion, a panel of experts says.

Considered a leading threat to the environment, soil erosion results when nutrient-rich top soil is washed away by water or swept up by wind. Vetiver, when planted in rows across steep slopes, keeps soil and water from flowing past.

Experts on soil erosion and specialists on the vetiver plant, who collaborated on a recent study for the National Research Council, said that vetiver's roots, which are 6 to 10 feet deep, hold the grass barrier and soil in place from below while the plant's tall blades of grass form a barricade against runoff above ground. Best Conditions for Plant

Able to grow in acidic or alkaline, fertile or infertile, waterlogged or parched soils, vetiver does not deprive crops of nutrients or space. Its sharp grass blades do not seem to harm livestock but do discourage them from eating or disturbing the vetiver hedge, said Dr. Noel D. Vietmeyer of the research council, who directed the study.

Vetiver, believed to be native to India, grows best in tropical and subtropical areas where rainfall is heavy but frosts are rare. The researchers said the grass hedge is able to grow in drier climates, like those in areas of Africa, and in cooler but not freezing climates, like those in areas in the Southern United States.

The grass can take from a few months to a year to grow deep enough and tall enough to combat soil erosion produced by water. Generally, however, it is less effective against erosion caused by wind unless the grass is planted close together to form a dense wind barrier, the study said.

Some scientists say grasses were planted in various parts of the world to limit soil erosion as early as the 1920's. The new study, primarily financed by the Agency for International Development, was begun because vetiver has remained "unloved and unrecognized as a means of preventing soil erosion," said Dr. Vietmeyer. "It needed credibility."

Other plants that have been used to prevent soil erosion, like the vine kudzu, grow so rapidly and wildly that they become uncontrollable nuisances. He said vetiver was a self-leveling grass that grows tall enough to block erosion but does not grow out of control and, in that way, interfere with crops the way that kudzu, weeds and some other grasses do.

Vetiver is not effective in most of the United States, especially in parts of Iowa where the soil, among the richest in the world, is eroding at one of the fastest rates in the world, said Dr. David Pimentel, a professor of entomology at Cornell University who was an author of the new study.

He said the vetiver research findings should not detract from the importance of crop rotation and other erosion-control techniques that can be used alone in colder climates or in conjunction with vetiver in warmer areas. Dr. Pimentel said it takes 200 to 1,000 years to replace one inch of topsoil. "Once topsoil is lost, you cannot sit around and wait for it to correct itself," he said.

Dr. W. Doral Kemper, who directs the research unit on soil and water conservation for the Agriculture Department, is studying other methods to control soil erosion. He said rows of vetiver and other grasses should be planted more widely because the method was described about 50 years ago and works well. He said he was looking for other grasses that would withstand colder climates, like those in the Northern United States and Canada.

The researchers said that since a simple row of vetiver could keep large amounts of water on crops longer, they grow faster and denser. Dr. Vietmeyer said that in a poor economy when farmers tend to live hand to mouth, they see little incentive to protect the land from damage that might not become apparent for another decade.

"Increased moisture in the soil makes the crops and trees grow better," he said. "To the farmer struggling to feed his family this year, that may be the only important reason to plant vetiver."

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A version of this article appears in print on February 16, 1993, on Page C00004 of the National edition with the headline: An 'Unloved' Grass May Turn Hero In the Struggle Against Soil Erosion. Order Reprints|Today's Paper|Subscribe